DE1671270B2 - PROCESS FOR GAS SEALING CONNECTING CERAMIC COMPONENTS - Google Patents

Abstract

1,173,386. Ceramic seals. WESTINGHOUSE ELECTRIC CORP. 26 April, 1967 [30 June, 1966], No. 19145/67. Heading B3V. [Also in Division C1] A method of sealing ceramic or refractory metal members to ceramic members comprises applying a sealing composition to the members, securing the sealing areas together, and heating the assembly to secure a bond, the composition of the sealing material after the sealing operation being, by weight per cent: and 0.5-10% of at least one of: SiO 2 BaO, ZrO 2 , SrO, TiO 2 , BeO, ThO 2 , Y 2 O 3 . Also included may be 0À5-3À5% by weight of Nd 2 O 3 , Ta 2 O 5 , W0 3 , Nb 2 O 5 , V 2 O 5 . A chart is included listing examples. The method may be applied to sealing Ta, Nb or ceramic, e.g. alumina, discs 12; 14 or caps on the ends of high-temperature metal vapour lamps 10 of alumina. Alumina rings 24, 26 are sealed to the discs 12, 14. One method preparing the sealing composition includes mixing 1 mole of CaCO 2 with ¢ a mole of alumina in powder form and adding the selected other constituents. Amyl acetate and cellulose acetate are included to obtain the desired viscosity and adhesion, and the composition is applied by brushing or spraying, after sand-blasting and cleaning the metal. The seals are air-dried before the assembly is located in a molybdenum clamping fixture, Fig. 2, having a tantalum R.F. susceptor 40. Alternatively, the sealing composition may be formed into compacted preforms. The fixture is placed on a rod. 48 within the R.F. coil of a vacuum furnace and subjected to a heating schedule, Fig. 3 (not shown). Another method of preparing the sealing composition to avoid a degassing period in the furnace includes melting the composition in a gas crucible furnace, pouring the molton mixture into water, ball-milling the mixture in distilled water to a fine powder, adding amyl acetate and cellulose acetate and subjecting the mixture to ultrasonic vibrations. A different firing schedule, Fig. 4 (not shown), may then be used. After evacuation of the tube 10 and insertion of the discharge sustaining filling, the tantalum tube 18 is closed and welded at 22. The expansion ratio of the tube 10, end plates and the sealing material match each other.

Description

5. The method according to claim 2, characterized

indicates that a sealant containing 2.5 percent by weight of Y ₈ O ₃ and the additional oxide in a total amount of 0.5 percent by weight is used as the modifying substance.

6. The method according to claim 2, characterized in that the invention relates to a method for gas-tight that a modifying substance 50 connecting components made of ceramic or high-3 percent by weight Y ₂ O ₃ and the additional oxide of melting metal with ceramic components, in a total amount of 3 percent by weight is used in particular for gas-tight joining of sealant-containing sealing compound. parts made of ceramic or refractory metal

7. A method, in particular for gas-tight electrical high-connection of ceramic components made of poly- 55 temperature metal vapor lamps with ceramic discharge tubes, in which one of at least niobium or tantalum according to one of claims 6, 40 percent by weight of Al ₂ O ₃ , at least 44 percent by weight of the one of the finely divided percent CaO and optionally at least one mixed component of the sealing compound of the modifying substances SiO ₂ , BaO, ZrO ₈ and SrO with the addition of a liquid carrier and ßo existing sealing compound The components produced on the sealing surfaces of a viscosity-imparting agent are applied and the paste together is applied to the sealing surfaces of the components and the assembled components

are heated to a temperature in the range of 150O ⁰ C, characterized in that the joined and ^{heated to dryness through to 70O 0} C and degassed at an average temperature of 80O ⁰ C for 20 minutes, then from a temperature of 900 ° C heated at a rate of change of 40 ⁰ C per minute in a period of 15 minutes to a temperature between 1450 and 155o ° C and 1 minute are kept at this temperature and then for 20 minutes with a change rate of 30 ⁰ C per minute finally to room temperature be cooled down.

8. A method, in particular for the gas-tight connection of ceramic components made of polycrystalline aluminum oxide with components made of niobium or tantalum according to one of claims 1 to 6, in which a paste made from the components of the sealant with the addition of a liquid carrier and a viscosity-imparting agent is applied to the Sealing surfaces of the components is applied and the assembled components ^{are heated to a temperature in the range of 1500 0} C, characterized in that the paste is ground from a to a particle size of less than 80 sieve openings per centimeter, by pouring a containing the components of the sealing compound Melt in water obtained frit is produced and that the assembled components in a vacuum furnace in 3 minutes from room temperature to 700 ⁰ C and then in 20 minutes with a rate of change of 40 ⁰ C per minute from 700 ⁰ C to a temperature between 1425 and 1550 ° C heated and one Minutes are kept at this temperature and then cooled from this temperature with a rate of change of 30 ⁰ C per minute to 700 ⁰ C and finally to room temperature.

a jig held components together in a vacuum furnace at room temperature first Joined components are heated to an elevated temperature at which the sealing compound connects the components and then cooled down.

Numerous masses have already been used to seal ceramic bodies, especially ceramic ones Bodies with high alumina content applied to refractory metals. Basically these were

3 4

Efforts on the sealing of either kera- Will the process of gas-tight joining of mix or of metallic decides or sealing parts made of ceramic or high-melting point -Caps directed to ceramic lamp bodies, the metal with ceramic discharge tubes electrical made of sintered, polycrystalline aluminum oxide, used in high-temperature metal halide lamps, see above high density in concentrations in the order of 5 are sealing parts made of ceramic with high of 99.5%. These dich- alumina or refractory metals like tantalum or niobium, except that they prefer a good bond. The additions to modiergiven, The thermal inherent lamps also improve the fiering substances of this type during the discharge applied high temperatures and the shafts of the almost eutectic calcium oxide-aluminum occurring Resist alkali metal vapors. Ver io minium oxide sealants as well as the mechanical Searches have been made to provide such lamps with strength of the bond.

using alloys from a titanium- Of additional importance in the manufacture Nickel composition as a metallic binding agent for vacuum-tight ceramic seals material and of vitreous masses that z. B. Aluminum high-temperature metal halide lamps are the burning minium oxide and one or more of the connections 15 temperatures and the timing of the process. Calcium oxide, barium oxide or strontiam oxide near- The following are preferred embodiments contained in eutectic percentages, to play the invention with reference to drawings poetry. explained. And that shows

So it is from US Pat. No. 32 43 635 and FIG. 1 a section through a high temperature

British patents 7 97 573 and 9 61 070 20 metal halide lamp to explain a use

known, the z. B. consisting of niobium final example of the sealing process according to the

caps of lamp bodies made of polycrystalline invention,

Aluminum by means of vitreous sealing compounds from FIG. 2 an attachment for use in

Seal Al ₂ O ₃ and CaO. These alkaline earth oxides seal ceramic components to metal ends

serve only as basic components of a 25 plate in a vacuum furnace,

Eutectic, the percentage composition of which is F i g. 3 shows a firing diagram of an exemplary embodiment

to a significant extent still from modifying the process for the manufacture of seals from

Substances such as B. BaO, MgO, SrO depends. Such ceramic materials on metals according to the invention

Sealants have the disadvantage that they are used for Rekristai- and

! ization and devitrification tend to cause cracks. 4 a firing scheme of another execution

can form, which due to reactions with, for example, the process for the production of sealing

the alkali metal vapors of the discharge lamps to gene from ceramic substances to metals according to the

premature failure of the lamps lead to the present invention.

can. On the other hand, since metallic binding materials are one of the main uses of the present

for stresses at higher temperatures in the 35 invention consists in sealing end plates or

Range of 150O ⁰ C are not suitable, these caps were attached to high-temperature metal halide lamps

Disadvantages so far consciously accepted. in Fig. The type shown in FIG. 1 General

In contrast, the invention has the object of a metal halide lamp shown consists of an Ent process for gas-tight connection of components charge tube 10, made of sintered polycrystalline aluminum Ceramic or refractory metal using high density 40 minium oxide on the one at each end specify a vitreous sealant, in which tantalum or niobium end disks or caps 12 and Recrystallization and devitrification at high temperatures 14 are sealed and sealed, which is preferably doors are avoided. have a thickness of about 0.1 to 0.38 millimeters.

On the basis of the course explained in more detail at the outset, these end disks can also consist of a

Method, the invention solves this problem by 45 ceramic material, for example a ceramic

that a sealant is used which is made of material with a high alumina content

44 to 55 percent by weight CaO, 40 to 50 percent by weight. Each of the end plates 12 and 14 is on the inner one

Percent Al ₂ O ₃ and 0.5 to 10 percent by weight of a surface with wound tungsten electrodes 16

or more of the modifying substances SiO ₂ , BaO, and on the outer surfaces with conductive supply lines

ZrO ₂ , SrO, TiO ₂ , BeO, ThO ₂ and Y ₂ O ₃ . 50 components 18 or 20 equipped. The feed component 18

In contrast to the known method, it has the shape of a tantalum tube, which extends through one made of aluminum and calcium oxides extends the end plate 12; he enables the Eve eutectic used, the only by kuierung the interior of the discharge tube 10 and modifying small amounts of oxides. By bringing in the entertaining the discharge the percentage filler to be used according to the invention in the metal halide lamp. After Parts of the components of the sealant are evacuated and charged to the metal halide lamp Not only compatible expansion coefficients, the supply line component 18 becomes Wi- by means of a spacing capability against alkali vapors at high quenching and welding clamped at 22. Short Temperatures and processability at acceptable support rings 24 and 26 made of polycrystalline aluminum temperatures Achieved, but there are also 60 minium oxide are also on the outer surfaces Recrystallization and devitrification at high temperatures of the end disks 12 and 14, respectively, sealed. If becherturen safely avoided. like caps in place of the end caps shown

The raw materials used are preferably made of raw materials or stock, which are made of aluminum oxide

masses of the standing support rings according to the invention are not necessary.

The sealing compounds used in the process are essentially 65 If the discharge tube 10 of FIG. 1 sealed

made of pure calcium carbonate and pure tet, the matching surfaces become

Aluminum oxide, both in very fine powder form and between the discharge tube 10, the end plates 12

the selective additions of modifying substances. and 14 and the support rings 24 and 26 with a

sr

paste-like form of the sealing compounds described below and coated during the in the F i g. 3 and 4 shown firing schemes, for example by means of a molybdenum attachment of the in Fig. 2 held together.

In order to obtain a vacuum-tight seal, the sealing material must be used on both the discharge tube 10 as well as the end disks 12, 14 wet at the right time It must be ensured that the thermal expansion coefficients of the three different Materials, d. H. the ceramic discharge tube, the metallic end plates and the sealing compound, close together to avoid failure due to thermal stress. Furthermore, the seal must be chemically inert to metal vapors and be adequate Have bond strength.

For example, there is the stock mixture that makes up the various alternative embodiments of the sealing compounds are derived, essentially atis 1 mol of a pure calcium oxide and 0.5 mol pure aluminum oxide, both in very distant powder form. A selected smaller percentage of one or more of the later is added to this stock mixture executed modifying oxides added. The ingredients are mixed thoroughly and then in an organic carrier material, for example Amyl acetate, suspended. A few drops of a viscose.tat granting agent, for example an organization Cement, such as B. cellulose acetate are added to increase the green strength of the mass. then the mixture is stirred until a paste-like consistency is reached. The sealant is then applied to the lead component 18 its point of contact with the central hole, η the end plate 12 and on the touching Flats of the support ring 26 of the Endsche.be 14. of the discharge tube 10, the end plate 12 and the Auflager.nges 24 broken open and the arrangement in burned in the manner described below, so that the high temperature vacuum device between the combined parts results. For the professionals it is it goes without saying that the sealing compound is applied to the respective surfaces by brushing or spraying or by using compact

SS £ ^ Jr ££ Lighter mechanical bond strength and better flux action, put together and held together until sk are air dry before being placed in a specially designed molybdenum clamp mount for firing.

The in F i g. 2 bracket attachment shown generally consists of a support member 30 from which Holding rods protrude 32 h. The support part 30 also carries a centering plug 34 on which a ceramic spacer 36 is attached to one end. The assembled metal halide lamp is placed on the ceramic spacer 36. To ensure even heat distribution ensure, a metal stamp 37 is attached to the support ring 24 at the other end. A second ceramic spacer 38 is mounted on metal stamp 37. A high frequency recording part 40 made of tantalum is attached around the assembly; it is attached to the support rods 32 by a pair set retaining clips 42 held. A fastening head 44 is slid over the support rods 32 and screwed against the ceramic spacer 38. To fix the arrangement will be Mounting screws 46 are screwed onto the upper end η of the mounting rods 32. The support part 30 of Clamp attachment is then placed on a support rod 48 in a high frequency heating coil in which the sealant, which is now in dry form on the matching surfaces of the arrangement is present, is heated according to a suitable firing schedule

A firing scheme for the sealants described above is shown in FIG. 3 shown. After that The composite discharge tube is placed in the fixture and the fixture is placed in a vacuum furnace

was performed on the support bar 48, the assembly is heated rapidly from room temperature to 700 ⁰ C in 3 minutes. The furnace is then held at an average temperature of 800 ^° C. for 25 minutes during a degassing period.

Then the oven temperature of 900 ⁰ C to 1450 to 1550 C is increased at a rate of 4O ⁰ C per minute for a period of 15 minutes. The arrangement is bS e £ ST mperätür between 1450 and 1550 ⁰ C for one minute

held and then at a rate of 3O ⁰ C

In (J ₂ or BeO is modified. The binder and pouring agent additive is mixed in fine powder form with AUO ₃ and CaO and the mass obtained is thoroughly mixed and then burned as described below, filtered and processed in my ball mill. Em organic carrier , for example amyl acetate, is added to the mixture to form a thin paste, and a few drops of a viscosity-imparting agent, for example cellulose acetate, are added to achieve the desired viscosity and dry adhesion.

or a load of 50 watts per Quadraientimeter operated without a SchädiinTder rods entered Furthermore mUNatrhim were filled metal halide lamps with polycrystalline Amminiumoxyd-Entiadungsrohren for more than 3000 hours at 400 Watth "ASkllSL S account the?

TURNING THE WATER BARRELS sen and manufactured according to the above scheme were fired above scheme

£ 35Ϊ

sealing surfaces of the parts, and the parts while the mass in paste form is still moist

tung fritted. After mixing the stock for a longer period of time, the well-mixed mass is placed in a recrystallized alumina crucible and ^{melted in a gas crucible furnace at 1600 to 165O 0} C. This molten glass is then fritted by pouring it directly onto water, then for 75 ground for up to 100 hours in distilled water and worked on the ball mill until the particle size of the glass is reduced to less than 160 sieve openings per centimeter. However, a size less than 80 screen openings per centimeter is generally considered sufficient for the production of a satisfactory sealant. Amyl acetate and cellulose acetate are then added as described above. In a LJItraschail vibration treatment, the coagulated particles are dispersed until a finely divided and uniformly mixed paste is obtained. The assembled metal halide lamp is then placed in the posture fixture and placed in a vacuum oven according to the procedure shown in FIG. 4 shown Brennsc hem ι heated.

After the in F i g. Firing schedule shown 4, it is required that the composite metal halide lamp from room temperature to 700 ° C in 3 minutes, heated as above, is then heated from 700 to 1425 to 155o ° C at a rate of 4O ⁰ C per minute for 20 minutes. The assembly is then held at a temperature of 1425 to 1550 ° C. for a period of one minute. After this mounting, the arrangement is cooled down from the holding temperature at a rate of 3O ⁰ C per minute to 700 ° C, then where the furnace turned off and the arrangement of the cooling is left to room temperature.

The sealants made excellent seals of polycrystalline alumina discharge tubes to end caps or end plates made from both ceramic materials such as alumina and metal when made and fired according to the methods described above. These sealing compounds further improve the mechanical strength of the bond and the vacuum sealing quality ^{of the metal-to-aluminum ox: d seals.} One group of these sealing compounds consists of 1 mol CaO and 0.5 mol Al ₂ O ₃ with the addition of 0.5 to 10 percent by weight SiO ₂ and 0.5 to 3 percent by weight of one or more of the materials Ta ₂ O ₅ , WO ₃ , Nb ₂ O ₅ and Nd ₂ O ₃ . Another group of sealing compounds that behaved equally well consisted of the basic compound of Al ₂ O ₃ and CaO with the addition of 0.5 to 10% Y ₂ O ₃ . This yttrium oxide sealing compound can also be used to improve the vacuum seal quality and the mechanical strength of the compound by adding 0.5 to 3 percent by weight of one or more of the substances Nd ₂ O ₃ , Ta ₂ O ₈ , WO ₃ , Nb ₂ O ₅ and V ₂ O ₅ to the sealant can be improved. These sealants can be molded and fired using any of the sealing methods listed above.

In the following table, 28 specific examples of the final ingredients are various Sealants listed after sealing according to one of the above methods. The specified Percentages indicate the percentage by weight of the finished sealant.

O O

\ D Tj-

~ O

so uT
■ *

CJ ff

OO C3

cn * o "

t 'ίο O

'η

Ό Ο

O"

in <N

cn in

°. ^c r— m 5 in in he ■ n • n E. Os "U ^- θ "S £ o "r · O" a " ⁰ - * χ > 4 ι -I TH C. 3 m • g m O' Q -o ■ * en C.
3 ensetz
3 E cn
β rs ^ O C 2 _r <■ , <n r-f • n cn " in cn " in CN

Sc?

ί d s d

S o ⁵

I i

609519/307

Each of the contemplated embodiments of the various sealing compounds enables a seal from aluminum oxide to aluminum oxide or from aluminum oxide to niobium or tantalum at high Temperature in high temperature gas discharge lamps. The sealants make good mechanical ones Bond strengths and show no harmful effects during prolonged operation from the in general Metal dampers used in this type of discharge lamp. Furthermore, each of the different Masses have a coefficient of temperature expansion that

10

substantially corresponds to that of niobium or tantalum and the polycrystalline alumina discharge tube. It follows from the above that the sealing _{compound contains the basic components Al 2} O ₃ and CaO in almost eutectic proportions in addition to one or more oxide additives and has not yet reached the fritted and powdered compounds, fired according to the respective firing schemes Strength and uniformity of the seals in high-temperature metal halide lamps result.

1 sheet of drawings

Claims (4)

Patent claims: 1. A method for gas-tight connection of components made of ceramic or refractory metal with ceramic components, in particular for gas-tight connection of sealing parts made of ceramic or refractory metal with ceramic discharge tubes of electrical high-temperature metal vapor lamps, in which one of at least 40 percent by weight Al ₂ O ₃ , at least 44 percent by weight CaO and optionally at least one of the modifying substances SiO ₂ , BaO, ZrO ₂ and SrO existing sealing compound is applied to the sealing surfaces of the components and the assembled components are heated to an elevated temperature at which the sealing compound connects the components and then cooled, characterized in that a sealing compound is used which consists of 44 to 55 percent by weight CaO, 40 to 50 percent by weight Al ₂ O ₃ and 0.5 to 10 percent by weight of one or more of the modifying substances SiO ₂ , BaO, ZrO ₂ , SrO, TiO ₂ , BeO, ThO ₂ and Y ₂ O ₃ "5. 2. The method according to claim 1, characterized in that a sealing compound is used which additionally contains 0.5 to 3.5 percent by weight, based on the total weight of CaO, Al ₂ O ₃ and the modifying substances, at least one of the oxides Nd ₂ O ₃ , Ta ₂ O ₅ , WO ₃ , Nb ₂ O ₅ and V ₂ O ₆ . 3. The method according to claim 1 or 2, characterized in that a sealing compound containing _{3 percent by weight of SiO 2 as a modifying substance is used.} 4. The method according to claim 2, characterized in that a _{sealing compound containing 2.5 percent by weight of SiO 2} and the additional oxide in a total amount of 0.5 percent by weight is used as a modifying substance.